Hadith 2:196

Narrated 'Aisha:

"When the prayers were first enjoined they were of two Rakat each.
Later the prayer in a journey was kept as it was but the prayers for
non-travellers were completed." Az-Zuhri said, "I asked 'Urwa what
made Aisha pray the full prayers (in journey)." He replied, "She did
the same as 'Uthman did."